Air conditioning system including reheat coils



R. F. LAUER 3,316,730

AIR CONDITIONING SYSTEM INCLUDING REHEAT COILS May 2, 1967 2Sheets-Sheet l Filed Jan. ll, 1966 ATTORNEY R. F. LAUER 3,316,730

AIR CONDITIONING SYSTEM INCLUDING REHEAT COILS May 2, 1967 2Sheets-Sheet 2 Filed Jan. ll. 1966 RODNEY F. LAUER, BYMJ-QMM ATTORNEYUnited States Patent C) 3,316,730 AIR CONDITIONING SYSTEM INCLUDINGREHEAT COILS Rodney F. Lauer, Staunton, Va., assignor to WestinghouseElectric Corporation, Pittsburgh, Pa., a corporation of PennsylvaniaFiled Jan. 11, 1966, Ser. No. 519,901 6 Claims. (Cl. 62-173) Thisinvention relates to air conditioning systems in which reheat is usedfor increasing the sensible heat of air which has been chilled, fordehumidication, to a temperature which is too low for comfort, and hasas an object to improve such systems.

In many locations, the wet bulb temperature of the outdoor air isfrequently so high that where the utmost in comfort is desired, it isnecessary to operate an air cooling system to chill the air to be cooledbelow its dew point temperature, and then to reheat the air to acomfortable temperature. This has been accomplished in many ways,including using the heat in recirculated air in so-called by-passsystems, and using the heat for condensers of refrigeration systems.This invention improves the latter systems.

In one embodiment of this invention using a nonreversible refrigerationsystem, an expansion valve, preferably a sub-cooling control valve,meters refrigerant liquid to an associated evaporator coil at the rateat which refrigerant is condensed in an associated condenser coil. Thisresults in over feeding the evaporator coil, and to prevent refrigerantliquid from flowing into the associated compressor, the gas andunevaporated refrigerant from the evaporator is tlowed into anaccumulator in which gas is separated from the liquid and supplied tothe suction side of the compressor. The liquid from the condenser coilflows through a heat exchange coil Within the accumulator before it issupplied to the sub-cooling control valve, the heat from the highpressure liquid flowing through such coil evaporating the excessrefrigerant liquid flowing from the evaporator coil into theaccumulator. A reheat coil is connected through a solenoid-controlledvalve to the discharge side of the compressor, and when reheat isrequired, the solenoid-controlled valve is opened to supply dischargegas into the reheat coil to operate it as an auxiliary condenser coil.The reheat coil is connected to the evaporator coil through a xedrestrictor which may be a capillary tube. Thus, when reheat is required,the reheat coil and its restrictor are connected in parallel with thecondenser coil and its sub-cooling control valve.

In a heat pump embodying this invention, the operation is that describedin the foregoing during cooling operation. During heating operation, thereheat coil operates continuously as a condenser coil, aiding in heatingthe indoor air.

This invention will now be described with reference to the annexeddrawings, of which:

FIG. l is a diagrammatic view of an Vair conditioning system using anon-reversible refrigeration system, embodying this invention, and

FIG. 2 is a diagrammatic view of a heat pump embodying this invention.

Description of Fig. l

The discharge side of a hermetic refrigerant compressor C, driven by anenclosed electric motor CM, is connected by discharge gas tube 10 to oneend of condenser coil 11, the other end of which is connected by tube12, heat exchange coil within the lower portion of accumulator 16, tube17, sub-cooling control valve 18 and tube 19 to one end of evaporatorcoil 20. The other end of the coil 20 is connected by tube 21 to theupper portion of the accumulator 16. U-shaped tube 22 within the ac-3,316,730 Patented May 2, 1967 cumulator 16 has an open upper end 23,and its other end is connected by suction gas tube 24 to the suctionside of the compressor C. Portions of the tubes 12 and 24 are in heatexchange Contact.

A fan 26 driven by an electric motor 27, moves indoor air to be cooledover the evaporator coil 20. A fan which is not shown, could be used tomove outdoor air over the condenser coil 11 when the latter is an aircooled coil.

The discharge gas tube 10 is also connected through tube 30 and valve 31to one end of reheat coil 32, the other end of which is connectedthrough a restrictor 33 shown as a capillary tube, to the tube 19. Therestrictor 33 could be a high pressure oat or a steam trap. The reheatcoil 32 is adjacent to and downstream with respect to air flow, of theevaporator coil 20.

The valve 31 is adjusted by a solenoid 3S which is connected by wire 36to electric supply line L1, and by wire 37 to switch TS2 of dry bulbthermostat T. The switch TS2 is connected by wire 38 to electric supplyline L2. Switch TS1 of the thermostat T is connected by wire 40 toswitch HS or humidistat H, and to one end of winding 41 of compressormotor starter MS, the other end of which is connected by wire 43 to theline L2. The switch TS1 is connected by wire 44 to the switch HS, and bywires 45 and 46 to the line L1. The switch TS1 of the thermostat T, andthe switch HS of the humidistat H are connected in parallel with eachother, and in series with the motor starter winding 41 to the lines L1and L2 so that either switch, when closed, can energize the starter MS.The starter MS has switches MSS which connect, when closed, through thewires 46 and 43, the compressor motor CM to the lines L1 and L2.

The sub-cooling control valve 18 has a diaphragm chamber 48, the outerportion of which is connected `by capillary tube 49 to thermal bulb 50in heat exchange Contact with the tube 12, and the inner portion ofwhich is connected by capillary tube 51 to the interior of the tube 12.The valve 18, the details of which are disclosed in the U.S. Patent No.3,171,262 of J. R. Harnish which issued on March 2, 1965, responds tothe temperature and pressure of the high pressure refrigerant within thetube 12, and meters refrigerant to the evaporator coil 20 at the rate atwhich the refrigerant is condensed within the condenser coil 11, whilemaintaining a predetermined amount of subcooling in the condensedrefrigerant.

Operation of FIG. I

The motor starter MS is energized by the closing of the humidistatswitch HS when the relative humidity of the indoor air is above, forexample, 50%, or by the closing of the thermostat switch TS1 when theindoor temperature increases above, for example F., and closes itsswitches MSS, starting the compressor motor CM. Discharge gas issupplied from the compressor C through the tube 10 into the condensercoil 11. Liquid flows from the coil 11 through the tube 12, the coil 15within the accumulator 16, the sub-cooling control valve 18 and the tube19 into the evaporator coil 20. The valve 18 operates to supply to thecoil 20 all of the refrigerant condensed within the condenser coil 11while maintaining, for example, 10 F. sub-cooling of the liquid flowingfrom the coil 11 at a condensing temperature of F., and is preferred forthis reason. However, a conventional expansion valve controlled by ahigh pressure pilot float meters refrigerant at the rate at which it iscondensed, and may be used, without the sub-cooling advantage. Theevaporator coil 20 is overfcd by the valve 18 so that gas andunevaporated refrigerant liquid ow from the evaporator coil into theaccumulator where the excess refrigerant liquid is evaporated by heatfrom the high pressure liquid flowing through the coil 15, the liquidbeing further subcooled by this action. Gas separated from the liquidwithin the accumulator ows through the suction gas tube 24 to thesuction side of the compressor C. Any liquid which may enter the tube 24is evaporated by the heat exchange between the contacting portions ofthe tubes 12 and 24, the liquid flowing through the tube 12 beingfurther subcooled by this action.

When the humidistat H is in control of the compressor C, the indoor airmay be chilled to such a low temperature that reheat is required. Whenthis happens, the switch TS2 closes at, for example, 78 F., andenergizes the solenoid 35 which opens the valve 31 to supply dischargegas from the compressor C through the tube 30 into the reheat coil 32 tooperate the latter as an auxiliary condenser for heating the indoor airchilled by the evaporator coil 20. The refrigerant condensed within thereheat coil 32 is expanded through the restrictor 33, and is suppliedinto the evaporator 20. The heat from the coil within the accumulator 16evaporates the excess refrigerant liquid fed from both the reheat coil32 and the condenser coil 11. Advantages of overfeeding the evaporatorare that its internal surfaces are thoroughly wetted, and distributionis not critical. Therefore, its eiciency is increased. There is noenergy loss in evaporating the excess refrigerant liquid by heat fromthe high pressure liquid flowing through the coil 15 within theaccumulator 16 since such high pressure liquid is subcooled by thisaction.

Description of FIG. 2

Those components of FIG. 2 which correspond to components of FIG. 1 aregiven the same reference characters.

Compressor motor CM drives compressor C. The latter is connected by tubeto a conventional reversal valve RV, adjustable by a solenoid RVS. Thevalve RV is connected by tube 60 to one end of indoor air coil IAC, theother end of which is connected by tube 61, tube 62 containing acheck-valve 63, and sub-cooling control valve 18 to the outlet of coil15 within accumulator 16. The valve 18 has a diaphragm chamber 48, theupper portion of which is connected by a capillary tube 49 to thermalbulb 50 in contact with tube 12, and the lower portion of which isconnected by capillary tube 51 to the interior of the tube 12. The inletof the coil is connected by tube 12, tube 65 containing a check-valve66, and tube 67 to one end of outdoor air coil OAC, the other end ofwhich is connected by tube 68 to the valve RV. The valve RV is connectedby tube 69 to the upper portion of the accumulator 16. The accumulator16 contains a U-shaped tube 22 having an open upper end 23, with itsother end connected by suction gas tube 24 to the suction side of thecompressor C. Portions of the tubes 12 and 24 are in heat exchangecontact. A tube 30 containing a valve 31 adjustable by a solenoid 35 isconnected to the tube 10 and to one end of reheat coil 32, the other endof which is connected by restrictor 33 to the tube 62 between the valve18 and the check-valve 63. The tube 67 is connected by tube 70containing a check-valve 71 to the tube 62 between the valve 18 and thecheck-valve 63. The tube 65 is connected by tube 72 containing acheck-valve 73, to the tube 61. The reheat coil is located adjacent toand downstream of the indoor air coil IAC. A fan 26 driven by anelectric motor 27, moves indoor air over the coils IAC and 32. A fan,which is not shown, could be used to move outdoor air over the outdoorair coil OAC.

The compressor motor CM is connected by wires 77 and 78, and switchesMSS of starter MS to electric supply lines L1 and L2 respectively. Thestarter MS has an energizing winding 80 connected by the wire 78 to theline L2, and connected by wire 81 to switches S1 and S2. The switch S1is also connected by wire 82 to switch TSl'of indoor thermostat T whichis connected across switch HS of indoor humidistat H. The switches TS1and HS are connected in parallel with each other and in series with theswitch S1 and the winding 80 of the motor starter MS to the supply linesL1 and L2. The solenoid 35 is connected by wire 36 to the line L2, andby wire 37 to switch TS2 of the thermostat T, which switch is connectedby wire 84 to the line L1. Switch S4 is connected by wire 85 to the wire37, and by wire 86 and the wire S4 to the line L1. The reversal valvesolenoid RVS is connected by wire 87 to the line L2, and by wire 88 toswitch S3 which is connected by wire 89 and the wires 86 and 84 to theline L1. Switch TSS of the thermostat T is connected to the wire 84 andto the switch S2.

The switch S1 is closed by switch blade B1 attached to insulator rod 90of cooling-heating control ,91, when control knob 92 on the right end ofthe rod 90 lis add justed to place the control 91 in cooling position asshown by FIG. 2. The switch S2 is on the opposite side of the blade B1from the switch S1, and is adapted to be closed by the blade B1 when thecontrol knob 92 is moved to the right of the position shown by FIG. 2,to adjust the control 91 to heating position. The switch S3 is closed byswitch blade B3 when the control 91 is in its cooling position as shownby FIG. 2. The switch S4 is adapted to be closed by switch blade B4 whenthe control 91 is in its heating position. The blades B3 and B4 are alsoattached to the rod 90. An indicator arrow 94 on the rod 90 is oppositea fixed indicator arrow 95 when the control 91 is in cooling position asshown by FIG. 2, and is opposite a xed indicator arrow 96 when thecontrol 91 is in its heating position.

The reversal valve RV is of the type which, when its solenoid RVS isdeenergized, is in its heating position, and when its solenoid isenergized, is in its cooling position.

Operation of FIG. 2

When indoor air cooling is desired, the control 91 is placed in itscooling position as shown by FIG. 2. The switches S1 and S3 are closed,and the switches S2 and S4 are open. lThe switch S1 connects thethermostat switch TS1 and the humidstat switch HS to control thecompressor motor starter MS. The switch S3 energizes the reverasal valvesolenoid RVS which adjust the r'ei versal valve RV to its coolingposition. The starter MS is energized by the closing of the switch HSwhen the relative humidity of the indoor air is too high, or by theclosing of the switch TS1 when the temperature of the indoor air is toohigh, and starts the compressor motor CM. Discharge gas from thecompressor C flows through the tube 10, the reversal valve RV and thetube 68 into the outdoor air coil OAC operating as a condenser coil.Condensed refrigerant ows from the coil OAC through the tube 67, thetube 65, the check-valve 66, the tube 12, the coil 15, the subcoolingcontrol valve 18, the tube 62, the check-valve 63 and the tube 611 intothe indoor air coil IAC operating as an evaporator coil. Gas andunevaporated refrigerant flow from the coil IAC through the tube 60, thereversal valve RV and the tube 69 into the accumulator 116. Gasseparated from the liquid within the accumulator ows through the tube 22and the suction gas tube 24 to the suction side of the compressor C. Thesubcooling control valve 18, and the coil 15 operate as described in theforegoing in connection with the operation of FIG. l.

When reheat is required, the thermostat switch TS2 closes and energizesthe solenoid 35 which opens the valve 31, supplying discharge gas fromthe tube 10` through the tube 30 into the reheat coil 32, operating thelatter `as a condenser coil for heating the air blown by the fan 26 overthe indoor air coil IAC. Refrigerant condensed in the reheat coil 32 isexpanded through the restrictor 33 and flows through the tube 62 andcheck-valve 63 into the indoor air coil IAC which is operating as anevaporator. Gas and unevaporated refrigerant flow from the coil IAC intothe accumulator 16 and from there the gas separated from the liquid owsto the suction side of the compressor as described in the foregoing.

When indoor air heating is required, the control 91 is placed in itsheati-ng position by moving the control knob 92 to the right so that theindicator arrow 94 lines up with the indicator arrow 96. The switches S1and S3 are opened, and the switches S2 and S4 are closed. The now openswitch S1 disconnects the thermostat switch TS1 and the hurnidistatswitch HS from control of the motor starter MS. The open switch S3deenergizes the reversal valve solenoid which adjusts the reversal valveRV to its heating position. The closed switch S2 connects the thermostatswitch TSS to control the starter MS. The closed switch S4 energizes thesolenoid 35 which opens the valve 31 so that discharge gas is suppliedinto the reheat coil 32 to operate it Aas a condenser coil during all ofthe heating operation.

When the thermostate T calls for heat, the switch TSS closes andenergizes the motor starter MS which closes its switches MSS, startingthe compressor motor CM. Discharge gas flows from the compressor Cthrough the tube 10, the reversal valve RV and the tube 60 into theindoor air coil IAC operating as a condenser coil. Refrigerant condensedwithin the coil IAC tiows through the tubes 611 and 72, the check-valve73, the tube 12, the coil 15 within the accumulator 16, the tube 62, thesubcooling control valve 18, the tube 70, the check-valve 71 and thetube 67 into the outdoor air coil OAC operating as an evaporator coil.Discharge gas also iiows from the tube through the tube 30 and the valve31 into the reheat coil 32 operating as a condenser coil. Refrigerantcondensed in the reheat coil 32 is expanded in the restrictor 33, andflows through the tube 70, the checkvalve 71 and the tube 67 into theoutdoor air coil OAC operating as an evaporator coil. Gas andunevaporated refrigerant flow from the coil OAC through the tube 68, thereversal valve RV and the tube 69' into the accumulator 16. Gasseparated from the liquid within the accumulator 16 iiows through thetubes 22 and 24 to the suction side of the compressor C. The subcoolingcontrol valve 18, and the coil within the accumulator 16 operate asdescribed in the foregoing in the description of FIG. 1.

The reheat coil 32 operating as a condenser coil, adds its heat to thatprovided by the indoor air coil IAC operating as a condenser coil,facilitating the heating of the indoor air.

What is claimed, is:

1. An air cooling system comprising a refrigerant compressor; acondenser coil; an evaporator coil; a discharge gas tube connecting saidcompressor to said condenser coil; accumulator means; a heat exchangecoil arranged to heat liquid within said accumulator means; la suctiongas tube connecting said accumulator means to said cornpressor; a liquidtube connecting said condenser coil to said heat exchange coil; anexpansion valve; a fourth tube connecting said heat exchange coil Itosaid valve; a fifth tube connecting said valve to said evaporator coil;a sixth tube connecting said evaporator coil to said accumulator means;means for moving air to ybe cooled over said evaporator coil; a reheatcoil adjacent to and downstream with respect to air flow of saidevaporator coil; a seventh tube connecting said discharge gas tube tosaid reheat coil; a normally closed valve in said seventh tube;expansion means connecting said reheat coil to said fifth tube; meansfor opening said normally closed valve when reheat is required and forreclosing said normally closed valve when no reheat is required; a-ndmeans for adjusting said expansion valve to supply refrigerant from saidheat exchange coil to said evaporator coil at the rate at whichrefrigerant is condensed in said condenser coil.

2. An air cooling system as claimed in claim 1 in which said expansionvalve is a subcooling control valve, and in which said means foradjusting said expansion valve responds to the pressure and thetemperature of the refrigerant in said liquid tube.

3. A heat pump for conditioning indoor air, comprising a refrigerantcompressor; an outdoor coil; an indoor coil; accumulator means; a heatexchange coil arranged to heat liquid within said accumulator means;means for moving indoor air over said indoor coil; a reheat coiladjacent to and downstream with respect to air flow of said indoor coil;an expansive valve; expansion means; control means; means including saidcontrol means, when air cooling is required, for directing refrigerantfrom said compressor in a first circuit through said outdoor coiloperating as a condenser, said heat exchange coil, said expansion valve,said indoor coil operating as an evaporator, and said accumulator meansto said compressor; means including said control means when reheat isrequired while refrigerant is flowing in said iirst circuit, fordirecting refrigerant from said compressor through said reheat coil andsaid expansion means into said indoor coil; means including said controlmeans when air heating is required, for directing refrigerant from saidcompressor in a second circuit through said indoor coil operating as acondenser, said heat exchange coil and said expansion valve into saidoutdoor coil operating as an evaporator, and from said compressorthrough said reheat coil and said expansion means into said outdoorcoil, from said outdoor coil into said accumulator means, and from saidaccumulator means to said compressor; and means for adjusting saidexpansion valve to supply refrigerant to said indoor coil when it isoperating as an evaporator and said outdoor coil is operating as acondenser, at the rate at which refrigerant is condensed in said outdoorcoil, and to supply refrigerant to said outdoor coil when it isoperating as an evaporator and said indoor coil is operating as acondenser, at the rate at which refrigerant is condensed in said indoorcoil.

4. A heat pump as claimed in claim 3 in which said expansion valve is asubcooling control valve, and in which said means for adjusting saidexpansion valve responds to the pressure and the temperature of therefrigerant flowing into said heat exchange coil.

5. A heat pump for conditioning indoor air, comprising a refrigerantcompressor; refrigerant reversal means; a discharge gas tube connectingsaid compressor to said reversal means; an outdoor coil; an indoor coil;accumulator means; a heat exchange coil arranged to heat liquid withinsaid accumulator means; a suction gas tube connecting said accumulatormeans to said compressor; a third tube connecting said reversal means tosaid accumulator means; a fourth tube connecting said reversal means tosaid outdoor coil; a fifth tube containing rst check-valve meansconnecting said outdoor coil to said heat exchange coil; an expansionvalve; a sixth tube connecting said heat exchange coil to said expansionValve; a seventh tube containing second check-valve means connectingsaid expansion valve to said indoor coil; an eighth tube connecting saidindoor coil to said reversal means; means for moving air over saidindoor coil; a reheat coil adjacent to and downstream with respect toair flow of said indoor coil; a ninth tube containing a normally closedvalve connecting said discharge gas tube to said reheat coil; meansincluding expansion means connecting said reheat coil to said seventhtube between said expansion valve and said second check-valve means; atenth tube containing third check-valve means connecting said seventhtube between said expansion valve and said second check-valve means tosaid fifth tube between said rst check-valve means and said outdoorcoil; an eleventh tube containing fourth check-valve means connectingsaid seventh tube between said second check-valve means and said indoorcoil to `said fifth tube between said rst checkvalve means and said heatexchange coil; means for adjusting said reversal means to coolingposition for routing discharge gas from said discharge gas tube throughsaid fourth tube into said outdoor coil to operate the latter as acondenser; means for opening said normally closed valve when reheat isrequired while said reversal means is in cooling position, for routingdischarge gas from said discharge gas tube through said ninth tube intosaid reheat coil to operate the latter as a condenser, and for reclosingsaid normally closed valve when no reheat is required; means forconcurrently opening said normally closed valve and adjusting saidreversal means to heating position for routing discharge gas from saiddischarge gas tube through said eighth tube into said indoor coil andthrough said ninth tube into said reheat coil for operating said indoorand reheat coils as condensers; and means for adjusting said expansionValve to supply refrigerant to said indoor coil While said outdoor coilis operating as a condenser at the rate at which refrigerant iscondensed in said outdoor coil, and to supply refrigerant to 6. A heatpump as claimed in claim 5 in which said expansion valve is a subcoolingcontrol valve, and in which said means for adjusting said expansionvalve responds to the pressure and the temperature of the refrigerantowing into said heat exchange coil.

References Cited by the Examiner UNITED STATES PATENTS 2,770,100 11/1956Raney 62-173 2,952,898 9/1960 Gould et al. 62-173 X 3,139,735 7/1964Malkoff et al. 62-197 X 3,209,814 10/1965 Block 165-14 3,264,840 8/1966Harnish 62--173 said outdoor coil while said indoor coil is operating asl5 ROBERT A OLEARY7 prima, Enum-nen a condenser at the rate at whichrefrigerant is condensed in said indoor coil.

M, A. ANTONAKAS, Assistant Examiner,

1. AN AIR COOLING SYSTEM COMPRISING A REFRIGERANT COMPRESSOR; ACONDENSER COIL; AN EVAPORATOR COIL; A DISCHARGE GAS TUBE CONNECTING SAIDCOMPRESSOR TO SAID CONDENSER COIL; ACCUMULATOR MEANS; A HEAT EXCHANGECOIL ARRANGED TO HEAT LIQUID WITHIN SAID ACCUMULATOR MEANS; A SUCTIONGAS TUBE CONNECTING SAID ACCUMULATOR MEANS TO SAID COMPRESSOR; A LIQUIDTUBE CONNECTING SAID CONDENSER COIL TO SAID HEAT EXCHANGE COIL; ANEXPANSION VALVE; A FOURTH TUBE CONNECTING SAID HEAT EXCHANGE COIL TOSAID VALVE; A FIFTH TUBE CONNECTING SAID VALVE TO SAID EVAPORATOR COIL;A SIXTH TUBE CONNECTING SAID EVAPORATOR COIL TO SAID ACCUMULATOR MEANS;MEANS FOR MOVING AIR TO BE COOLED OVER SAID EVAPORATOR COIL; A REHEATCOIL ADJACENT TO AND DOWNSTREAM WITH RESPECT TO AIR FLOW OF SAIDEVAPORATOR COIL; A SEVENTH TUBE CONNECTING SAID DISCHARGE GAS TUBE TOSAID REHEAT COIL; A NORMALLY CLOSED VALVE IN SAID SEVENTH TUBE;EXPANSION MEANS CONNECTING SAID REHEAT COIL TO SAID FIFTH TUBE; MEANSFOR OPENING SAID NORMALLY CLOSED VALVE WHEN REHEAT IS REQUIRED AND FORRECLOSING SAID NORMALLY CLOSED VALVE WHEN NO REHEAT IS REQUIRED; ANDMEANS FOR ADJUSTING SAID EXPANSION VALVE TO SUPPLY REFRIGERANT FROM SAIDHEAT EXCHANGE COIL TO SAID EVAPORATOR COIL AT THE RATE AT WHICHREFRIGERANT IS CONDENSED IN SAID CONDENSER COIL.